Catheter

ABSTRACT

A catheter and associated method for taking a plurality of samples from within a length of a blood vessel. The catheter includes an elongate central body arranged to be inserted into and positioned along a central region of a blood vessel. A plurality of collection areas are defined along the elongate central body for collecting samples at the central region of the blood vessel. A plurality of mixers are provided radially outwardly of the elongate central body and arranged to create a flow of blood from a boundary layer at a wall of the blood vessel to the elongate central body. This enables the collection areas to collect samples from the boundary layer.

BACKGROUND TO THE INVENTION

The present invention relates to a catheter, in particular a catheterfor collecting a plurality of samples from within a length of a bloodvessel. The present invention further relates to associated methods, inparticular a method for generating a data profile for one or morebiomarkers emanating from the wall of a blood vessel, a method ofprofiling a length of a blood vessel to determine the pathological orphysiological state of the blood vessel wall, and a method of samplingblood in vivo from a blood vessel.

It is known from WO 2006/126002 to take a plurality of samples of bloodfrom along a length of a blood vessel. The samples are taken from nearto the vessel wall and can be analysed so as to determine concentrationsof biomarkers that are present there and hence to determine positions ofvulnerable plaque, etc. along the blood vessel along the length of thesampling part of the catheter.

Although such earlier arrangements are very useful and effective, theypresent difficulties depending on the configuration of the catheter andthe location and/or size of the vessel under test. For example, it isnot always practical to manoeuvre a sample collection area of thecatheter into position near to the vessel wall, due to the varyinggeometry of the vessel and constraints in positioning of the catheter.The present application seeks to obviate these difficulties and toimprove the consistency of results and obtain closer correlation betweenthe actual positions of sources of biomarkers and the positions at whichthose biomarkers are first sampled. As detailed below, this is achievedby inducing a flow from the boundary layer towards a sample collectionarea.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda catheter for taking a plurality of samples from within a length of ablood vessel, the catheter including:

-   -   an elongate central body arranged to be inserted into and        positioned along a blood vessel;    -   at least one collection area defined along the elongate central        body for collecting samples at the central region of the blood        vessel; and    -   at least one mixer provided radially outwardly of the elongate        central body and arranged to create a flow of blood from a        boundary layer at a wall of the blood vessel to the elongate        central body so as to enable the at least one collection area to        collect samples from the boundary layer.

The at least one mixer preferably creates a flow of blood towards thecollection area of the catheter so as to enable the at least onecollection area to collect samples representative of fluid materialpresent in the 360 degree radial section that defines the volume betweenthe catheter and the inner wall of the blood vessel.

The collected samples can be representative of the entire crosssectional area of the blood within the vessel, i.e. from the centre ofthe elongate central body to the blood vessel wall.

By virtue of the at least one mixer, components such as biomarkers,emanating from as far away as the wall of a blood vessel and theadjacent boundary layer can be brought rapidly to the collection areaalong the elongate central body of the catheter for sampling. As aresult, samples taken from a catheter (which has previously been placedin a blood flow) will more accurately reflect the actual position of thesource of those components such as biomarkers. Also, as a result ofbringing the flow to the at least one collection area more quickly andproviding a shorter longitudinal offset between the actual source ofbiomarker and the sample site for the biomarker, detection becomes moreaccurate, precise and sensitive. Furthermore, the longitudinal offsetbecomes more consistent thereby allowing for appropriate correction.

The term boundary layer is used to cover all types of boundary layersincluding both velocity boundary layers and diffusive boundary layers.

Samples of blood extracted from the vessel may contain biomarkers whichcan be defined as any characteristic that is objectively measured andevaluated as an indicator of normal biologic or pathologic processes orpharmacological responses to a therapeutic intervention where thecharacteristics could include whole blood, cells, cellular components,chemicals and molecules such as lipids, proteins, nucleic acids andmetabolic products.

Different types of mixer can be used, for instance brushes, sponges,foam, flaps, blades, paddles, helical sections, etc. However,preferably, at least one of the mixers is a static mixer.

This is advantageous, because a static mixer need not have any movingparts and can increase the rate of biomarker (or any blood component)diffusion across a wide range of flow conditions, from laminar toturbulent. Normally arterial flow is laminar and diffusion is very slow.A static mixer can be used to increase the diffusion of biomarkers, forinstance by splitting the flow in two, with the resultant fluid elementsbeing rotated by 90° in opposite directions to each other; and beingrecombined, the fluid elements having undergone a physical rotationrelative to each other. Such a split, rotate and recombine processbrings the biomarkers within the flow a step closer to the collectionarea. Repeating the process brings the biomarkers closer still andincreases the effect of diffusion on fluid homogeneity.

Although it is possible to provide mixers which are relatively small incross-section and, hence can be moved into position within a bloodvessel in their normal state, preferably, the at least one mixer isdeployable from an inactive state in which the at least one mixer isclose to the elongate central body for insertion into a blood vessel andis deployable to a plurality of active states in which the at least onemixer is further away from the elongate central body so as to interferewith a boundary layer of the blood vessel.

In this way, in the inactive state, the catheter has an overall smallcross-sectional area facilitating insertion into and along a bloodvessel. The mixer is then deployable to its active state so as to bettermix blood within the blood vessel.

The mixer may also engage (depending on the internal diameter of thevessel at that point) and conform to the wall of the artery. This canact to control the deployed diameter of the mixer in the absence of anyother constraining force, for instance from a sheath.

Preferably, the mixer is able to deploy to an appropriate extent fromthe elongate central body so as to best interfere with the boundarylayer which is along the wall of the blood vessel (such as artery) andpotentially contains different concentrations (relative to the freestream or bulk flow of blood) of biomarkers emanating from the wall orabsorbed into the wall as might be expected at locations ofheterogeneous biological activity. For some diameters of blood vessel,this might mean that the mixer extends so as to meet with the wall ofthe blood vessel, whereas for larger diameter blood vessels, this mightmean that the mixer moves to a position only close to the wall of theblood vessel.

Embodiments are possible where the at least one mixer extends on oneside of the elongate central body. Depending on the nature of the mixerit may be desirable then to include at least one other mixer whichextends on the opposite side of the elongate central body. However,preferably, the at least one mixer extends circumferentially around theelongate body in substantially all radial directions. In this way, it ispossible for the mixer effectively to mix blood from any position of theperiphery of the blood vessel. Preferably, the at least one mixer thuscan create a flow of blood from the boundary layer around the entireperiphery of the blood vessel.

Although the mixer can be embodied as a single component, the at leastone mixer can comprise a respective plurality of mixing elementsextending radially from the elongate central body.

It is possible for the plurality of mixing elements of the at least onemixer together to form an extent circumferentially around the elongatecentral body in substantially all radial directions.

Each mixing element could be fixed relative to the elongate centralbody. However, optionally each mixing element is pivotably attached tothe elongate central body so as to pivot in the elongate direction ofthe elongate central body and towards and away from the elongate centralbody. In other words, each mixing element pivots about an axisperpendicular to the elongate direction or at least angled with thatelongate direction.

In this way, in effect, each mixing element can be folded down to aninactive state resting against or close to an outer surface of theelongate central body. Alternatively, each mixing element can be pivotedup and away from the elongate central body to an active state. Theextent to which mixing element is pivoted away from the elongate centralbody can be varied according to the diameter or internal extent of theblood vessel in which it is inserted.

Each mixing element could be formed from a respective component separateto the elongate central body and be mounted to the elongate central bodyby any appropriate pivoting mechanism. Alternatively, at least a portionof the mixing element at the point at which the mixing element isattached to the elongate central body is made of an appropriate flexiblematerial.

Optionally, each mixing element has the form of a paddle extending inradial and tangential directions with respect to the elongate centralbody.

The paddle could be considered as a fin or flap which extends outwardlyfrom the longitudinal surface of the elongate central body so as todisrupt blood flow in the blood vessel and cause mixing. Hence, themixing element has a longitudinal extent which extends in at leastpartly a radial direction with respect to the elongate central body. Onthe other hand the lateral extent of the mixing elements extends in adirection parallel to tangents from the outer surface of the elongatecentral body.

It is possible for each mixing element to be angled relative to thelongitudinal axis of the elongate central body so as to take the form ofa blade of a propeller and to direct the blood flow in a predeterminedcircumferential or spiral direction according to the direction of angle.

Optionally, the mixing elements are arranged at successive positionsalong the elongate central body and, thus, are spaced apartlongitudinally along the length of the elongate central body. Atsuccessive positions along the elongate central body, the mixingelements may be positioned at corresponding successive angles around theelongate central body.

In this way, when a mixing element at a first position along theelongate central body causes blood flow to be divertedcircumferentially, subsequent mixing elements along the length of theelongate central body are positioned at different radial positions so asto interfere with different parts of the cross section of the bloodvessel around the elongate central body. In particular, it is possiblefor the diverted flow from one mixing element to flow into the mixingelement arranged at the next elongate position.

Optionally, the relative angle around the elongate central body betweenmixing elements at adjacent positions along the elongate central body issubstantially 90°.

Thus, after each mixing element splits or diverts blood flow along theblood vessel, the next mixing element is offset by substantially 90° soas to divert a 90° offset portion of the cross-section of the bloodvessel. This arrangement works particularly well with mixing elementshaving a radial extent of substantially 90°. For mixing elements havingsmaller radial extents themselves, the relative position betweensuccessive mixing elements can be a smaller radial angle. It ispreferable for the radial extent of the mixing elements to slightlyexceed the radial angle therebetween, so that there is some overlap ofsuccessive mixing elements when viewed axially.

Optionally, the mixing elements are arranged in pairs, each pair ofmixing elements being positioned at a respective position along theelongate central body and individual mixing elements of a pair of mixingelements being on opposite respective sides of the elongate centralbody. In other words, a pair of mixing elements might include one mixingelement extending above an elongate central body and another mixingelement extending below the elongate central body. Where successivemixing elements are at corresponding successive angles, the next pair ofmixing elements could have one mixing element extending to one side ofthe elongate central body and the other mixing element extending to theother side of the elongate central body.

It is possible to use only one pair of mixing elements. However,optionally, the at least one mixer includes at least two such pairs ofmixing elements.

This provides a good compromise between providing an excessive number ofmixing elements and giving sufficient mixing.

Additional pairs of mixing elements could be provided to furtherincrease the quality of mixing. Certainly, good results can be achievedwith 3, 4 or 6 pairs.

In order to place the mixer in the inactive state, it is possible todeflect each of the mixing elements so as to be substantially flatagainst the outer surface of the elongate central body. Preferably themixing elements are shaped and spaced such that when they are deflectedin this way, mixing elements at adjacent positions along the elongatecentral body substantially do not overlap. With this arrangement, theprofile of the catheter is minimised, thus improving movement of thecatheter to a target site.

It is also possible to arrange for outer portions of the mixing elementsto be thinned or profiled such that the overlapping of adjacent mixingelements does not take up undue radial depth.

The collection areas can be arranged in any known or appropriate mannerfor collecting samples. However, the at least one collection areaincludes at least one collection port located at a respective positionalong the elongate central body for collecting a respective sample atthat position. Samples collected at that position will, of course, be ineffect a sample collected from the boundary layer prior to mixing.

It is possible to provide catheters with a variety of different arraysof mixers and collection areas. For example, a plurality of collectionareas can be provided for each mixer. Similarly, each collection areacould include a plurality of collection ports. However, in a preferredembodiment, a single collection port is provided between adjacentmixers. A collection port may be provided at a position upstream of anymixing so as to provide a sample of unmixed blood to be analysed forpurposes of normalization.

The collection ports may provide ports for sampling in any known orappropriate manner, for instance opening to sampling pockets which mightoptionally include absorbing material. However, in one embodiment theelongate central body includes at least one lumen extending internallyalong the elongate central body connecting with the at least onecollection port.

The lumen forms a volume into which a sample of blood may flow from therespective collection port. The lumen can be pre-filled with saline orequivalent. Natural blood pressure may be used in order to allow asample to be collected in the lumen. Alternatively, low pressure may beapplied to an opposite end of the lumen so as to draw blood in throughthe respective collection port. The lumen may be coated withanticoagulation materials, e.g. heparin, phosphorylcholines.

Optionally, the elongate central body includes a plurality of lumensextending internally along the elongate central body connecting withrespective collection ports. In this way, a plurality of samples, forinstance one sample between each mixer, can be taken at the same time.

In order to reduce the mixing requirements for the mixers, it ispossible to use mixers which merely create a flow of blood from aboundary layer to the elongate central body without necessarily mixingblood throughout the entire cross-section around the elongate centralbody. This means that blood flow from a boundary layer at one side of ablood vessel may only be presented to that same side of the elongatecentral body. To ensure that samples of this blood flow are taken, itwould be possible to provide a plurality of collection ports around theperiphery of the elongate central body. However, in one embodiment, atthe at least one collection area, the elongate central body includes anouter wall having an outwardly facing surface and an inwardly facingsurface and an inner body in which the at least one collection portionis defined. The inwardly facing surface of the outer wall and the innerbody can define a circumferential gap therebetween. A circumferentialarray of through holes can be defined through the outer wall between itsinwardly facing surface and its outwardly facing surface. Thecircumferential gap can then form a manifold for feeding the at leastone collection port from a plurality of radial directions.

In other words, a flow of blood from the boundary layer at any positionaround the periphery of the blood vessel will be provided to theelongate central body. By providing the through holes spaced around theentire periphery of the elongate central body, it should always bepossible, by means of at least one of those through holes, to take asample of the blood flow to include samples representative of the 360degree segment around the catheter.

Because the through holes are all connected to the collection port bymeans of the manifold, the collection port is thus able to collect anappropriate sample, even if the blood flow from the boundary layer isprovided to an opposite side of the elongate central body to that of thecollection port.

Optionally, the catheter is provided with a sleeve within which theelongate central body and the at least one mixer can be stowed. Bywithdrawing the sleeve the at least one mixer and the at least onecollection area can be exposed.

In one embodiment, exposing the at least one mixer allows that mixer tomove from its stowed inactive state to a deployed active state.Preferably, by moving the sleeve back over the elongate central body themixers can be moved back to their stowed inactive state.

According to a second aspect of the present invention, there is provideda method for generating a data profile for one of more biomarkersemanating from the wall of a blood vessel, which method comprisesanalysing a plurality of blood samples from a bloodstream that has beenmixed substantially across the radial extent of the blood vessel toinclude blood present in the boundary layer at the blood vessel wall,the blood samples being taken at respective locations along a length ofthe blood vessel, the analysis including the steps of:

-   -   measuring a concentration level of a biomarker in each blood        sample;    -   determining a first concentration correction factor for each        respective blood sample to correct for differences in sample        volume and dilution between different blood samples;    -   determining a second concentration correction factor to correct        for a measured background concentration level for the biomarker        present in general circulation within the bloodstream;    -   for each blood sample, applying a respective first and the        second concentration correction factor to the measured        concentration level of the biomarker in each blood sample to        determine a corrected concentration level of the biomarker; and,    -   generating a data profile of corrected concentration levels for        the biomarker along the length of the blood vessel.

Optionally, the method further comprises the step of analysing at leastone blood sample collected from an upstream location to determine thesecond correction factor to be applied to the measured concentrationlevels of the biomarker.

Optionally, blood samples are analysed to measure the concentration of areference marker in general circulation in the bloodstream having aknown or measured concentration, whereby a respective first correctionfactor is calculated for each blood sample to correct for differencesbetween the measured concentration of the reference marker in the bloodsample and that in general circulation.

Optionally, blood samples are taken from within a coronary artery and atleast one blood sample taken from an aortic arch.

According to a third aspect of the present invention, there is provideda method of profiling a length of a blood vessel to determine thepathological state or physiological state of the blood vessel wall,comprising the steps of:

-   -   introducing into a blood vessel a flexible vascular catheter        having a body section provided with a plurality of blood        collection ports for collecting samples along a length of the        blood vessel;    -   deploying at least one mixer radially outwardly of the catheter        body, the mixer thereby mixing blood substantially across the        radial extent of the blood vessel to include blood present in a        boundary layer at the blood vessel wall;    -   collecting blood at the blood collection ports downstream of the        at least one mixer;    -   analysing blood collected by the blood collection ports of the        catheter to determine a data profile of the concentration levels        of one or more biomarkers along the length of the blood vessel.

According to a fourth aspect of the present invention, there is provideda method of sampling blood in vivo from a blood vessel, comprising thesteps of:

-   -   introducing into a blood vessel a flexible catheter having a        body section provided with a plurality of blood collection ports        for collecting samples along a length of the catheter;    -   deploying at least one mixer radially outwardly of the catheter        body, the mixer thereby mixing blood flowing within the blood        vessel substantially across the radial extent of the blood        vessel; and,    -   collecting blood at one or more blood collection ports        positioned downstream of the mixer for subsequent analysis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription, given by way of example only, with reference to theaccompanying drawings, in which:

FIG. 1 illustrates schematically an embodiment of the present invention;

FIG. 2 illustrates schematically an alternative embodiment;

FIG. 3 illustrates schematically an alternative embodiment;

FIGS. 4( a) and (b) illustrate schematically alternative embodiments;

FIG. 5 illustrates a preferred embodiment of the present invention;

FIG. 6 illustrates an embodiment similar to FIG. 5 in cross-section;

FIG. 7 illustrates schematically a mixing element for use with thepresent invention;

FIG. 8 illustrates schematically an alternative mixing element for usewith the present invention;

FIG. 9 illustrates schematically an alternative mixing element for usewith the present invention;

FIG. 10 illustrates schematically a mixing element folded in a stowedposition;

FIG. 11 illustrates schematically mixing elements stowed adjacent oneanother;

FIG. 12 illustrates schematically two mixing elements folded together;

FIGS. 13( a) to (e) illustrate folding of wire structures for use withthe present invention;

FIGS. 14( a) to (e) illustrate the folding wire structures of FIGS. 13(a) to (e) from a different view;

FIG. 15 illustrates schematically an example of constructing a mixer;

FIG. 16 illustrates schematically an example of fitting mixing elements;

FIG. 17 illustrates schematically an alternative example of fixing amixing element;

FIG. 18 illustrates schematically a multi-lumen tube;

FIGS. 19( a) to (e) illustrate cross-sections of multi-lumen tubingsuitable for use in embodiments of the present invention;

FIG. 19( f) illustrates a cross-section of alternative multi-lumentubing suitable for use in another embodiment of the present invention;

FIG. 20 illustrates schematically a manifold for use in a preferredembodiment of the present invention;

FIG. 21 illustrates schematically a sheath for sealing with a manifold;

FIG. 22 illustrates schematically a sheath for sealing with a raisedportion of the catheter;

FIGS. 23( a) to (c) illustrate respectively for the same length of bloodvessel three different individual/groups or other combinations ofmolecules or biomarkers associated with different stages in plaqueevolution;

FIGS. 24( a) and (b) illustrate the concentration of biomarker presentat the central region of a blood vessel as a result of plaque, wherelittle or no mixing occurs within the blood vessel; and

FIGS. 25( a) and (b) illustrate the concentration of biomarker presentat the central region of a blood vessel as a result of plaque, wheremixing within the blood vessel is used.

DETAILED DESCRIPTION

The present invention concerns the provision of at least one mixer on acatheter for taking samples within a blood vessel. The at least onemixer is for creating a flow of blood from outer portions of the bloodvessel to an inner central region of the blood vessel where samples canbe collected by the catheter. For example, a plurality of samples may betaken along a length of a blood vessel such as a coronary artery, andthose samples analysed to detect biomarkers and thereby identifyvulnerable plaques and other phenomena releasing biomarkers into theblood flow of the blood vessel. Such phenomena might be damagedepithelial tissue, healed epithelial tissue and in general any localisedprocess in which biological or pharmacological processes are underwaye.g. tissue response to stenting, measures of drug uptake from drugreleasing stents, tissue response to balloon angioplasty, stent graftingand any other natural process or interventional procedure that mightcause a localised tissue response. In particular, it is desirable tocreate a flow from the boundary layer at the wall of the blood vessel tothe central region of the blood vessel. In this way, biomarkersresulting from plaque from the walls of the blood vessel can be sampledand detected by the catheter irrespective of the radial location of thecatheter within the blood vessel.

FIG. 1 illustrates schematically a length of a blood vessel 2 into whicha catheter 10 has been inserted. The catheter 10 includes an elongatecentral body 12 having a plurality of collection areas 14 along itslength. In this illustrated embodiment, each collection area 14 includesa respective collection port 16 for collecting an individual sample.However, the collection areas 14 may alternatively be embodied withother known means of taking samples, or indeed may include more than onecollection port for collecting respective samples.

As illustrated, a plurality of mixers 18 is also provided along thelength of the catheter 10. In particular, the mixers are providedradially outwardly of the elongate central body 12. The mixers 18 extendin a region of the blood vessel 2 at least close to the outer wall ofthe blood vessel 2 and the boundary layer at that wall.

It is sufficient to have only one mixer 18 upstream of a plurality ofcollection areas 14. However, with each additional mixer, mixing of theblood within the blood vessel 2 is improved such that the results ofsampling at the central region of the blood vessel can also be improved.Hence, it is desirable to provide a plurality of mixers 18 and these aremost advantageously distributed alternately between adjacent collectionareas such that each successive collection area is sampling a bettermixed volume of blood.

FIG. 1 illustrates a biomarker release stream 4, for instance resultingfrom plaque on the wall of the blood vessel 2. Biomarkers released intothe boundary layer will tend, if undisturbed, to remain in that boundarylayer such that optimal sampling by a catheter with collection areas inthe central region of the blood vessel 2 can be difficult to achieve.

It is possible that the catheter (for instance on a guidewire) isoff-centre. As will become apparent below, the mixers can have a secondfunction of biasing the catheter to the centre of the blood vessel (forinstance by their inherent resilience/stiffness acting against anyoff-centering force of a guidewire).

With a structure such as illustrated in FIG. 1, where a plurality ofsuccessive mixers 18 is provided, it is far from essential that eachmixer provide 100% mixing. It will be appreciated that for a mixer 18having 50% efficiency, the mixed portion of blood at successivecollection areas will be mixed by percentages of 50, 75, 87.5, 93.8,96.9, 98.4. Similarly, for mixers with efficiencies of 75% mixing willoccur with percentages of 75, 93.8, 98.4, 99.6, 99.9, 100 and for mixersof 90% efficiency with percentages of 90, 97.5, 99.4, 99.8, 100, 100.

By taking these mixing proportions into account, it will be possible topredict where, along the length of the catheter 12, the biomarkerrelease stream 4 emanates from. Of course, where the biomarker releasestream 4 and its associated plaque are positioned somewhere along thelength of the catheter 12, collection areas 14 upstream of the biomarkerrelease stream will not sample any biomarker at all (or at least willonly sample a background level).

In one embodiment, a collection area is provided upstream of any mixer18 such that an unmixed sample of the blood can be taken so as toprovide an indication of any background levels. The additional upstreamcollection area is highly advantageous in performing normalisation ofdata acquired from the samples.

The schematically illustrated mixers 18 of FIG. 1 can be embodied inmany different ways, for instance as lamina flow static mixers orturbulent mixers. A static mixer is a mixer that achieves its mixing bystaying still. It does not add energy to the system. It may work on bothlaminar or turbulent flow. A mixer that acts upon turbulent flow mayinclude a static mixer and requires that there is sufficient energywithin the flow to generate turbulent recirculation. In a mixer thatinduces turbulence as the core mechanism for mixing, it may do this byshearing the liquid or adding energy in the form of a secondary flow orpowered moving element. Preferably, the static mixer is optimised forlaminar flow mixing but ideally operates for all types of flow, i.e.laminar, and turbulent (best defined as Reynolds Numbers from 1×10−6 to10,000). The term laminar and turbulent is complex here as a turbulentflow may actually be considered laminar if the analysis scale ischanged, i.e. a turbulent flow path can be considered as being made upof lots of laminar sections going in different directions. Hence, at thescale of coronary arteries, although the pulses from the heart may beconsidered “turbulent”, the net flow characteristic within that arteryis best considered as being laminar.

Irrespective, in some embodiments, the mixers are deployable from afirst stowed and inactive state to a second deployed and active state.In particular, in some embodiments, the mixers 18 start in a stowedinactive state in which they are close to the outer surface of theelongate central body 12 such that the overall cross-sectional areapresented by the catheter 10 is relatively small. This allows thecatheter 10 to be inserted into the blood vessel 2 more easily. Once thecatheter 10 has been inserted into the desired region of the bloodvessel 2, the mixers 18 are then moved to their deployed and activestate. In this state, the mixers 18 extend outwardly toward the outerregions of the blood vessel 2 and the overall cross-sectional areapresented by the catheter 10 is increased.

It is possible to form a mixer from foam and FIG. 2 illustratesschematically a catheter 20 having deployed foam mixers 28.

FIG. 3 illustrates schematically an arrangement in which a catheter 30uses mixers 38 constructed from a plurality of fibres or bristles. Thefibres or bristles extend radially from the elongate central body 32.

It is preferable that mixers are able to operate within blood vessels ofa variety of different internal diameters. In this respect, it isdesirable that the deployed state of the mixers extends over a range ofdiameters. For smaller diameter blood vessels, the mixers 18, 28, 38extend from the elongate central body 12, 22, 32 and touch the wall ofthe blood vessel 2. To attain the desired mixing, it is sufficient forthe mixers to extend to a region close to the wall of the blood vessel 2and merely interfere with the boundary layer. Blood vessels are notuniformly sized and may be tapered. It is desirable for the catheter tobe able to function along the length of a blood vessel, irrespective ofthe internal diameter. Hence, by using deployable mixers, the mixers maybe deployed to differing extents to touch or extend close to the wall ofthe blood vessel no matter what the internal diameter of the bloodvessel at that point, within a certain range.

In certain arrangements, the mixers provide the desired mixingirrespective of the direction of flow. Also, where the mixers are bentover from the elongate central body towards the walls of the bloodvessel, it will be appreciated that they will be angled towards or awayfrom the direction of flow. Indeed, with the mixers in a deployed statesuch that their distal ends, or tips, meet with the walls of the bloodvessel, if the elongate central body is moved within the blood vessel,it is possible for the mixers to be deflected such that they movebetween states facing towards and facing away from the direction offlow. In view of this, preferred arrangements of the mixers operate formixing the flow irrespective of whether the mixers face into the fluidflow or face away from the fluid flow.

Certain embodiments of the present invention use static mixers, theseoffering the best potential for meeting size, deployment, mixing andmanufacturability requirements.

It is desirable to provide complete mixing whereby any biomarkerpropagates both about the circumference and radially through the bulkblood flow in the blood vessel.

In other fields of technology, fluid mixers have been proposed using aseries of helical sections, each helical section having an oppositedirection of twist with respect to the adjacent helical section.

FIGS. 4( a) and (b) illustrate two possible arrangements for staticmixers.

Each of the mixers of FIGS. 4( a) and (b) include a plurality of mixingelements which extend radially from the elongate central body.

In the mixer 48 of FIG. 4( a) four mixing elements 44, 45, 46 and 47 arearranged along the length of the elongate central body 42 of thecatheter 40. Each mixing element 44, 45, 46, 47 has a helical and screwshape so as to rotate the flow of fluid as it moves in the longitudinalsection of the elongate central body 42. As illustrated, each mixingelement rotates through 360° and each mixing element rotates in anopposite direction to any mixing element adjacent to it. In this way,while one mixing element causes fluid flow to rotate in one direction,when that fluid flow reaches the next mixing element, the fluid iscaused to change its flow and flow in the opposite direction. It will beappreciated that any number of mixing elements could be used as a mixer44 but that preferably two or more mixing elements are used. It shouldalso be appreciated that other arrangements could use similar mixingelements which rotate through more or less than 360°.

In certain arrangements such as illustrated in FIG. 4( a), the outwardflow of fluid from one mixing element is directed towards a surface ofthe mixing element of the next mixing element. In the illustratedembodiment of FIG. 4( a), this is achieved by one set of alternatemixing elements 44, 46 being rotationally offset relative to the otherset of alternate mixing elements 45, 47 by 90°.

In the arrangement of FIG. 4( b) the mixing elements 44, 45, 46, 47 ofthe arrangement of FIG. 4( a) are replaced by pairs of mixing elements54, 55, 56 and 57.

In the arrangement of FIG. 4( b), a helical, spiral or screw section isreplaced by two diametrically opposed, but relatively angled planarsections. Considering the pair of mixing elements 54, a first mixingelement 54 a extends from one side of the elongate central body 52 ofthe catheter 50 in the form of a 1800 sector for filling half of theinternal space of a blood vessel. The first mixing element 54 a passesthrough a diameter of the elongate central body 52, but is angledrelative to a plane perpendicular to the axis of the elongate centralbody 52. On the other hand, the second mixing element 54 b of the pairof mixing elements 54, while similarly being a sector passing throughthe diameter of the elongate central body 52 is angled oppositely to theplane perpendicular to the axis of the elongate central body 52. In thisway, the pair of mixing elements 54 functions crudely like a 360° spiralor helix. Preferably, at least one of the first and second mixingelements 54 a, 54 b is in the form of a sector just over 180° so thatthere is some overlap of the pair of mixing elements when viewedaxially.

As with the embodiment of FIG. 4( a), it is preferable that the outletof flow of one pair of mixing elements 54 flows into an opposing face ofthe next pair of mixing elements 55. Hence, as illustrated in FIG. 4(b), alternate pairs of mixing elements 54, 56 are arranged with respectto the other set of alternate pairs of mixing elements 55, 57 at anoffset angle of 90° about the axis of the elongate central body 52.

FIG. 5 illustrates a further arrangement where the mixing elements arearranged in pairs. However, in the arrangement of FIG. 5 the individualmixing elements of the pairs of mixing elements are arcuate sectors ofless than 180°. The mixing elements are still effective in causingrotation of the flow of fluid around the catheters and for causingopposing counter-rotation at different portions of the mixer along thelength of the catheter.

FIG. 5 illustrates a non-helical mixer. The mixing elements, or fins,are not tilted relative to the axis of the elongate central body (otherthan being slightly folded in).

As discussed above, it is desirable for the mixers to be deployable fromstowed positions close to the elongate central body of the catheter todeployed positions extended outwardly away from the elongate centralbody towards the outer periphery of a blood vessel.

By constructing the mixing elements of FIGS. 4( a) and (b) and of FIG. 5from appropriate materials at least where they are attached to theelongate central body, it is possible for those mixing elements to befolded down against the outer surface of the elongate central body.However, it is desirable to be able to stow the mixers in a more compactmanner than is possible with these arrangements. It will be appreciatedthat the extent of the mixing elements of the arrangements of FIGS. 4(a) and (b) means that the mixing elements themselves need to deform inorder to be folded against the outer surface of their correspondingelongate central bodies.

FIG. 5 illustrates one embodiment of the present invention allowing goodmixing and effective stowage of the mixers before deployment. FIG. 6essentially illustrates the arrangement of FIG. 5 in cross-section, butis in conjunction with a collection port of a type to be described ingreater detail below, in particular with reference to FIG. 20.

As illustrated, the mixing elements are arranged in pairs, withindividual mixing elements 124 a, 124 b of a pair 124 being arranged onopposite sides of the elongate central body 122 of the catheter 120. Theindividual mixing elements extend radially and circumferentially fromthe elongate central body 122 and form paddles or fins which are toextend to the internal outer periphery of a blood vessel. The mixingelements take the form of sectors of relatively small angular extent,for instance in the region of 90°. Each individual mixing element may begenerally planar and follow a plane extending through a diameter of thecentral elongate body 122. In an at rest state, opposing mixing elementsof a pair of mixing elements may extend outwardly perpendicular to theaxis of the elongate central body 122 and lie in a common plane. FIG. 5illustrates the mixing elements deflected in one longitudinal direction,whereas FIG. 6 illustrates those mixing elements deflected in anopposite longitudinal direction.

In the illustrated embodiment, adjacent pairs of mixing elements extendfrom the elongate central body 122 in different radial directions. Inthe illustrated embodiment alternate pairs of mixing elements extend inone radial direction, whereas the interleaved pairs of mixing elementsextend in a different radial direction, preferably at 90° to the firstalternate set of mixing elements. Thus, in the cross-section of FIG. 6,cross-section through opposing mixing elements 124 a and 124 b arevisible, whereas mixing element 125 b is not visible and only mixingelement 125 a is visible behind the elongate central body 122.

The advantage of the arrangement of FIGS. 5 and 6 is that the individualmixing elements are able easily to be folded along the length of theelongate central body 122 and wrapped partly around its periphery.

It will be appreciated that, although the embodiment of FIGS. 5 and 6includes six pairs of mixing elements, with individual mixing elementshaving a radial extent of appropriately 90° and alternate pairs ofmixing elements angled relative to one another by appropriately 90°,other similar arrangements are possible using mixing elements ofdifferent angular extent, using different numbers of mixing elements inany one group and using a different number of groups of mixing elementsalong the length of the elongate central body 122. In this regard, it ispreferable for the radial extent of at least one of the mixing elementsto slightly exceed the radial angle between the alternate pairs, so thatthere is some overlap of the mixing elements of successive alternatepairs when viewed axially. For example, a mixing element having a sectorof 1000 could be appropriate for this arrangement.

The arrangement allows there to be provided a deployable static mixerincluding at least two mixing elements that remain fixed within a bloodvessel so as to sequentially separate, rotate and re-combine fluid flowand so as to effect mixing across the radius of the blood vessel.Because of the symmetry of the arrangement, this will work with a fluidflow in either direction. Also, this will work with varying degrees ofmixing element angle, in other words the extent to which the mixingelements are folded down towards the elongate central body 122. Thesequentially placed groups of mixing elements induce counter-rotatingflows within the bulk fluid flow. By attaching the mixing elements tothe elongate central body 122 and hinging them near the axis of theelongate central body 122 and the blood vessel, the mixing elements maybe folded to adapt the mixer to a range of blood vessel diameters. Inother words, for small blood vessel diameters, the mixing elements willbe angled over towards the elongate central body 122, but, for largerblood vessels, the mixing elements may extend directly out from theelongate central body 122, perhaps not contacting the walls of the bloodvessel, but merely interfering with the boundary layer against thosewalls.

With the mixing elements folded against the elongate central body, aconcentric sheath or sleeve may be arranged around the catheter 120. Thesheath or sleeve may be withdrawn from the catheter 120 so as to exposethe mixing elements and allow the mixing elements to deflect outwardlyfrom a stowed position to an active position. After the catheter hasbeen used, the sheath or sleeve can then be pushed back over the mixingelements causing them to deflect back towards the elongate central body122 and fit within the sheath or sleeve in their stowed positions.

In one embodiment, the mixing elements function whether or not they faceinto or away from the fluid flow. Therefore, how the mixing elementsemerge from the sheath or sleeve is not important to functioning of themixer. Indeed, if the catheter 120 is moved axially within a bloodvessel such that the mixing elements are caused to be deflected betweenan orientation angled into or away from the fluid flow to the other ofinto or away from the fluid flow, functioning of the mixer is notimpeded.

In one embodiment, the mixing elements are flexible. Thus, optionally,the mixing elements are made with sufficient elasticity to provide thenecessary combination of both resilience and compliance to enable safeand effective use within a blood vessel. Optionally, this ensures thatthe outermost diameter of the mixing element, when deployed, makes aclose fit with the outermost diameter of the blood vessel withoutdamaging it or at least comes close to the wall of the blood vessel soas to interfere with its boundary layer. In addition, as mentionedabove, such deployable mixing elements may, due to their resilience, actto urge the catheter into a central position within the blood vessel.

The mixer elements can be constructed in a variety of different waysusing a variety of different materials while still meeting the basicrequirements of the invention. It is preferred for the mixing elementsto be able to deploy and function in blood vessels having internaldiameters in the range of 2.3 to 4.0 mm, and more preferably 2.0 to 5.0mm.

Optionally, the mixing elements are made from materials that providesufficient resistance to allow the mixing elements to deploy (forinstance upon retraction of a sheath) by expanding (in the manner ofbending outwardly from the elongate central body) until the mixingelement reaches full deployment or, alternatively, contacts the innerwall of the blood vessel. Optionally, the mixing elements are made frommaterials that, once deployed, exert a stiffness appropriate to resistthe flow of blood. However, they should be soft enough not to abrade ordamage the endothelial layer (inner wall) of the blood vessel.Optionally also the mixing elements are made from materials that enablethe mixer to be collapsed when subjected to a collapsing force by theoperator, for instance moving a sheath or sleeve over the deployedmixing elements and driving them to their stowed state.

Suitable materials are preferably bio-compatible and include medicalgrade elastomeric materials such as silicones, urethanes, thermoplasticvulcanizates, etc. It is also possible to use non-elastomeric medicalgrade materials by controlling their geometry, for instance, theircross-sectional area, to provide the appropriate stiffnesscharacteristics. Materials that can be injection molded, cast, solidfreeform fabrication (inkjet, SLA, etc), machined or deposited can beused to make the mixing elements.

The mixing elements can be formed from single materials, such as moldedelastomers, or may be cut and bent from a metal tube for instance madefrom a shape memory metal or polymer (for example nitinol). In thisregard, FIG. 7 illustrates a fin profile cut into the wall of a tube andthen folded out to form a fin or paddle forming a mixing element.

Mixing elements can also be made as a composite, with differentmaterials used for different parts of the mixing element. FIG. 8illustrates a root, mast or scaffold 130, for instance made from wire,such as flexible or shaped memory or super elastic wire. This connectsthe main body 132 of the mixing element to an elongate central body ofthe catheter. The main body 132 may be made from a different material,in particular that can conform to the circumference of a tube. It may beprovided with a tip 134 constructed from a very soft elastomer tominimise any damage to a blood vessel wall. The main body or sail can bemolded, cast or stamped.

FIG. 9 illustrates an arrangement where a main body 132 is formed from apolymer film wrapped around a scaffold 136 which extends to form theroot or mast and preferably has shaped memory and forms a super elasticwire frame or scaffold.

FIG. 10 illustrates schematically the main body 132 of a mixing elementin its stowed state and positioned between an elongate central body 122and an outer sheath 140. As illustrated, the flexible structure of themixing element allows it to conform to the outer surface or wall of theelongate central body 122.

Following on from FIG. 10, it will be appreciated that, in someembodiments, different mixing elements do not overlap with each other.In this respect, it is possible to use profiled edges, such asillustrated in FIG. 11 to prevent overlap of mixing elements when themixing elements are collapsed against the outer surface of the elongatecentral body.

It is also possible to use variable fin thickness to minimise the totalthickness of the mixing elements when sheathed. For instance, asillustrated in FIG. 12, a thinner fin profile is provided in the regionsof overlap of the mixing elements 132 a and 132 b.

FIGS. 13( a) to (e) and 14(a) to (e) illustrate a wire structure such asmentioned with reference to FIG. 9. A deployed state is illustrated inFIGS. 13( a) and 14(a). Successive Figures move to a fully stowed statewithin a sheath as illustrated in FIGS. 13( e) and 14(e). FIGS. 13( a)to (e) illustrate an end view of a catheter with wires 136 and sheath140 whereas FIGS. 14( a) to (e) illustrate a side view of the catheterwith wires 136 and sheath 140.

As illustrated, each wire structure 136 is able to fold into the sheath140 by collapsing the wire structure 136 in front of it. As describedabove with reference to FIG. 9, the wires can act as a frame to aflexible thin film and hence act as the mixing elements.

Various possibilities exist for constructing the catheter with themixing elements.

The mixing elements could be formed separately and then individuallystuck to the outer wall of the elongate central body. For example,adhesives, thermal bonding, shrink fitting or ultrasonic welding couldbe used to attach the mixing elements to the elongate central body.

Each mixer could be formed as an individual unit including all of itsmixing elements. For example, a mixer, including the mixing elementscould be over molded onto a pin of appropriate diameter, then removedand adhered to the elongate central body.

FIG. 15 illustrates schematically a plurality of mixing elements 124being over molded onto tubing 122. As illustrated, the mixer is beingover molded directly onto the elongate central body 122, but similarlythe mixer could be molded onto a forming pin and then transferred to theelongate central body 122.

In the arrangement of FIG. 16, individual mixing elements 124 or pairsof mixing elements 124 are attached to the elongate central body 122 bymeans of a tube, tape or other binding structure 150, for instance heatshrink tubing or adhesive lined shrink fit tubing. This structure couldactually be part of the manifold structure.

For mixing elements such as described with reference to FIGS. 8 and 9having masts, roots or the like for instance made from wires comprisedof materials with shape memory or super elastic properties (for examplemetals such as Nitinol or shape memory polymers as provided by companiessuch as in mNemoscience GmbH), it is possible to provide apertures 152in the elongate central body 122 into which those roots 130 can beinserted and fixed as illustrated in FIG. 17. Alternatively the mixingelements and their roots could be insert molded into the elongatecentral body 122. In other words, the elongate central body 122 isformed around the root 130 of the mixing element.

As illustrated in FIG. 7, it is also possible for individual mixingelements to be cut from the wall of the elongate central body and bentout to a desired angle. When manufactured from a shape memory polymer ormetal, this could be programmed with the desired stiffness anddeployment characteristics.

As discussed above, it is proposed to use a sheath, such as sheath 140for retaining the mixing elements in their stowed state. However, mixingelements could alternatively be self-actuating using shape memoryeffects via both shape memory metals and shape memory polymers.

As mentioned above, the described mixers could be used with anyappropriate catheter for taking multiple samples. However, a preferredembodiment is constructed using an elongate central body which is formedfrom multi-lumen tubing. In particular, the elongate central bodypreferably includes and defines a plurality of elongate passageways orlumens along its length each of which can be connected to a collectionport and used to collect a respective sample.

A variety of different designs of multi-lumen tubing which could be usedas part of an elongate central body of the catheter. FIG. 18 illustratesschematically a multi-lumen tube.

FIGS. 19( a) to (e) illustrate a variety of different multi-lumen tubearrangements, suitable for use with over-the-wire (OTW) catheterintroduction techniques.

As illustrated, the multi-lumen tubing includes a plurality of lumens160 arranged circumferentially around the periphery of the elongatecentral body, each lumen being suitable for connection to a respectiveconnection port and collecting a respective sample. In the illustratedembodiments, a central elongate hole 162 is also provided for receivinga guidewire for the catheter.

As illustrated, a variety of different arrangements are possible. FIGS.19( a) to (e) illustrate respectively elongate central bodies having tenlumens of 200 μm diameter, 8 lumens of 240 μm diameter, 5 lumens of 400μm diameter, 8 lumens of 400 μm and 10 lumens of 400 μm diameter. Choicefor a preferred embodiment depends on the priority between rate ofcollection, longitudinal spatial resolution and total cross sectionalarea of lumen. Priorities would be to minimise the diameter (ideallysuitable for use in a 2.00 mm (6F) or smaller guide catheter) thenmaximise the resolution and accept an extended time to collectsufficient volume. For use in conjunction with a 2.00 mm (6F) guidecatheter, the outside diameter of the catheter in the stowed positionwould be less than 1.5 mm.

FIG. 19( f) illustrates, schematically, an alternative multi-lumen tubearrangement suitable for use with rapid exchange (Rx) catheterintroduction techniques. In this arrangement, the collection lumens 160are offset with respect to a guidewire lumen 163. With thisconfiguration, the guidewire lumen can have an exit aperture for anassociated rapid exchange guidewire whereby the guidewire can exitwithout crossing any of the collection lumens 160.

Individual lumens 160 may be connected directly to respective collectionports at the outer surface of the elongate central body, for instance aswas illustrated schematically in FIG. 1. However, mixers may be usedwhich provide effective radial mixing on only one side of the elongatecentral body so as to carry biomarkers from the boundary layer of ablood vessel to the elongate central body. With such arrangements, if aconnection port happened to be positioned on the opposite side of theelongate central body to the source of biomarkers to be sampled, thenreduced sampling efficiency might occur.

FIG. 20 illustrates one arrangement in which the collection areaincludes an outer wall 170 surrounding the central elongate body 164 soas to define a circumferential gap or manifold 172 between the outerwall 170 and elongate central body 164. Through holes 174 are providedthrough the outer wall 170 at positions around the entire circumferenceof the outer wall 170 such that the manifold 172 communicates with fluidoutside the outer wall 170. This is also illustrated in FIG. 6. Acollection port 166 is provided in the outer surface of the elongatecentral body communicating with a respective lumen 160. The collectionport 166 is able to collect a sample from fluid in the manifold 172.However, since the manifold 172 communicates with fluid from around theentire periphery of the catheter by means of the through holes 174, thecollection port 166 is thus able to collect samples of biomarkers evenif these emanate from an opposite side of the catheter.

FIG. 20 illustrates an arrangement where only one collection port 166 isprovided for collecting samples in a respective collection area.However, it is also possible for others of the lumens 160 illustrated inFIG. 20 to connect to collection ports in the same collection area. Forinstance, two diametrically opposed lumens 160 could both connect torespective collection ports in the same collection area.

FIG. 21 illustrates schematically an arrangement using an outer wall 170where a single sheath 140 is used to deploy and constrain the mixingelements 124 and can also seal the through holes 174 of a manifold. Thesheath 140 holds the mixing elements 124 down and engages the raisedouter wall 170.

FIG. 22 illustrates schematically a similar arrangement without the useof a manifold where the collection port 166 is merely raised and extendsto a level to be engaged by the sheath 140.

In some arrangements, it may be desirable for the sheath 140 to sealwith the through holes 174 or collection ports 166. However, this is notessential in other arrangements, because the sampling can be controlledby pressure regulation of the lumens.

The lumens and the volume inside the sheath can be saline-filled so asto prevent bubble release when the sheath is retracted and the systemdeployed. It should be noted that blood pressure is usually sufficientto force blood into exposed lumens and will overcome any inherent airpressure/atmospheric pressure inside the lumens. However, it would bepossible to draw samples using negative pressure (relative toair/atmospheric pressure); this can accelerate the rate of flow.

Having obtained samples with the catheter, those samples may be removedfor analysis in any convenient manner. It is possible for the samples tobe withdrawn from the lumens using suction from either end. In onepreferred embodiment, the collection ports 166 or through holes 174 mayhave a size and shape suitable for receiving a standard laboratorypipette. Where the outer wall 170 is used with a plurality of throughholes 174 it may merely be necessary to close all but one of the throughholes 174 so as to withdraw a sample from the though hole 174 whichremains open.

There now follows a description of how a plurality of samples can beanalysed.

After a catheter for obtaining a plurality of samples has been insertedinto a blood vessel, such as a coronary artery, it is possible to obtainan image of the position of the catheter in the blood vessel.

The catheter may be inserted into a blood vessel using conventionalPercutaneous Coronary Intervention (PCI) techniques. Accordingly,catheters according to this invention may be introduced by means ofstandard PCI equipment, including introducers, guidewires and guidecatheters. Such introduction may be via over-the-wire (OTW) or via rapidexchange (Rx) techniques, the latter of which is preferred.

Sites of interest within a blood vessel under investigation can beidentified by a clinician using known techniques. For example, theclinician might inject contrast media in order to image the blood vesseland to determine sites of interest. Alternatively or additionally,standard imaging tools such as IVUS or the InfraRedx plaque locatingsystem could be used. Once the sites of interest have been identified,the catheter for obtaining a plurality of samples can be introduced asdescribed above. In the case of imaging tools that have been introducedinto the blood vessel over a guidewire, the catheter can be introducedfollowing the same guidewire, once the imaging tool has been removed.

The catheter may be tracked within the blood vessel using standardfluoroscopic techniques and may be provided with radio-opaque markersallowing the position of the catheter and each collection port to berecorded, for example as an image. The radio-opaque markers may belocated at key reference locations such as at the sheath tip and in theblood collection regions. Optionally, a radiopaque marker band may belocated adjacent to each blood collection port.

With this data, it becomes possible later to overlay the results of anyanalysis of the samples onto an image of the blood vessel.

When samples for a coronary artery are to be analysed, it is preferredthat the total length of sampling is sufficient to include the majorityof the length of the coronary artery and where possible a bulk flowsample from the aortic arch. Hence, it is preferred that the catheterhas been inserted previously into a coronary artery and aorta in thisway prior to samples being taken.

A plurality of blood samples obtained from a catheter can be tested formultiple proteins. By way of example, proteins can be chosen that arelinked in any way to the various stages of cardiovascular disease. Suchstages can include healthy endothelium, preliminary endothelium loss offunction, early inflammatory, late inflammatory, cap thinning,vulnerable plaque, leakage of thrombotic molecules, plaque rupture,plaque calcification and plaque stabilisation. Examples of possiblemolecules that are weakly linked with these different stages include

-   -   ICAM and VCAM-1    -   Soluble CD40L    -   any of the matrix metalloprotease family    -   Soluble E-selectin    -   Monocyte chemo attractant protein-1    -   Macrophage colony stimulating factor    -   P-Selectin    -   E-Selectin    -   Cathepsin S    -   Neutrophil elastase    -   Endothelial-leukocyte adhesion molecule-1    -   Intercellular adhesion molecule-1    -   Soluble Vascular cell adhesion molecule-1    -   Tissue Factor    -   Pregnancy associated plasma protein A    -   Protein-bound-Insulin-like growth factor    -   Neopterin    -   Soluble P-Selectin    -   IL-1, IL-6, IL-7    -   Choline    -   Heat Shock Proteins    -   Chlamydia pneumonia lipopolysaccharides    -   Degraded interstitial collagen from plaque (Type I+III)    -   TNF-alpha    -   Myeloperoxidase

The plurality of blood samples obtained from the catheter could also betasted for mRNA. mRNA is nucleic acid that is used as a temporaryinstruction to make the protein—it is a biological entity that instructsthe formation of a protein from the DNA instruction. It is possibleeither to look for the gene expression signal that instructs cells tomake the protein or to look for the protein itself.

With a catheter removed from its collection site, individual samples canbe extracted and retained in individual sample containers correspondingto and with reference to the length over which the samples werecollected.

Analysis is possible such that sensitivity will not be compromised bythis approach.

In one preferred system, a dilution factor of approximately 12-fold isproposed. Thus, for extracted samples of 2 μl, it is proposed to top upthe samples with 23 μl of assay buffer according to appropriate assayprotocols.

In one system, it is proposed to use the multiplex Luminex (trade mark)platform for detection purposes. According to this arrangement, multipledifferent classes of 6 μM beads are incubated with the diluted sampleand the proteins of interest are bound by antibodies fixed to the beads.The bound proteins are then detected bead by bead in a specialised flowcytometer. As part of this process, it is possible to use LINCOplex(trade mark) multiplex assays as provided by Linco Research Inc. Thisallows detection of a plurality of proteins simultaneously at lowpicogram/ml levels.

Thus, the extracted and diluted samples are analysed to look for proteinor nucleic acid or drugs using a highly multiplex assay such that manyanalytes can be measured within each sample. Systems for proteinanalysis, such as the Luminex system, will allow analysis of up to 100proteins at sensitivities of approximately one picogram/ml.

As part of preferred analysis of the extracted samples, the assay datais normalised to a reference analyte, such as a protein, present in eachsample. The reference protein is one having a concentration which can beexpected to be constant throughout the length of blood vessel in whichthe catheter had been used. In particular, it is a protein that is notproduced or absorbed in this region of the blood vessel. Examples,particularly for coronary arteries, include serum albumin or gammaglobulin. This additional “reference” protein assay will be run on eachseparate sample extracted from the catheter.

Data from any one assay can be used to determine the mass of aparticular protein in that corresponding sample by comparing thesample's data point against a predetermined reference curve. Because theconcentration of the reference protein can be assumed to be constant ineach sample, then the determined mass will be directly proportional tothe amount of sample volume assayed.

In this way, the data obtained for each biomarker for all of the samplesextracted from the catheter can be normalised by reference to thereference protein.

In one system, a volume correction value is determined by calculating anaverage of all of the reference values from all of the extractedsamples. The individual biomarker data can then be normalised withreference to this volume correction value. Optionally, each sample'sreference value is expressed as a fraction of the average referencevalue.

The volume correction value can then be used to adjust the data of allproteins in all samples so that it is possible to correct for variationsin volume transferred from the catheter. In particular, this is achievedby multiplying each raw data value by the correction factor.

The following table illustrates data for a series of eight samples (A toH) for analysis.

Blood extracted and assayed in e.g. a microtitre plate well A B C D E FG H Reference 17 15 16 17 19 21 16 17 protein amount from assay Averageref 17.25 17.25 17.25 17.25 17.25 17.25 17.25 17.25 amount across allassays Correction 1.01 1.15 1.08 1.01 0.91 0.82 1.08 1.01 factor Rawdata for 140 159 179 190 185 182 170 160 Biomarker 1 cone from assayCorrected 142 183 193 193 168 150 183 162 concentration of Biomarker 1Raw data for 4000 3790 3800 3960 4250 4700 3900 3870 Biomarker 2 conefrom assay Corrected 4059 4359 4097 4018 3859 3861 4205 3927concentration of Biomarker 2

As illustrated, raw data is available for a reference protein and alsofor biomarkers 1 and 2. Thus, for sample A, a value of 17 is obtainedfor the reference protein, a value of 140 is obtained for biomarker 1and a value of 4,000 is obtained for biomarker 2. Other values ofreference protein are obtained for other samples. For example, sample Ehas a value of 19 for the reference protein. Using this value for thereference protein, it would be possible to normalise the sample E rawdata of 185 for biomarker 1 and 4,250 for biomarker 2 with regard tosample A. In particular, for sample E, the biomarker raw data could bemultiplied by 17/19.

As illustrated, in this arrangement, an average reference amount isobtained for all of the samples by averaging the individual referencevalues for the reference protein across all of the samples. By comparingthe actual individual reference values for respective samples with theaverage reference amount, individual correction factors are obtained foreach sample. The correction factors can then be applied to the rawbiomarker data so as to normalise that data across all of the samples.

The corrected values for the biomarkers/molecules can be presented byany user interface, either numerically or graphically. A user can thenmake use of this data as required. In particular, molecularconcentrations could be compared with the most upstream sample port andexpressed as a relative difference.

In a case where a catheter has been inserted in a coronary artery,preferably the most upstream collection port samples from the aorticarch. It is then possible to show a differential of blood within thecoronary artery relative to blood incoming to the coronary artery.Samples taken from parts of the catheter which were adjacent torespective parts of the coronary artery show an increase in specificmolecules and thus the release of these molecules within those areas ofthe coronary artery as compared with levels in general circulation.

The catheter may be provided with radio-opaque markers to facilitatecorrelation of regions of biomarker heterogeneity with the location ofthe catheter within the blood vessel at time of capture. This enableslocalised regions of biological or chemical heterogeneity in a bloodvessel to be identified.

In one arrangement, the various information contained for the biomarkerscan be displayed directly in relation to positions along the bloodvessel, for instance the coronary artery.

As mentioned above, a catheter can be provided with radio-opaquemarkers. With an image of the blood vessel, such as the coronary artery,available, the particular biomarker values can be overlayed onto thatimage, either numerically or graphically. It is possible to provide anapparatus and a display for processing data appropriately and presentingthe data in this way. Appropriate computer programs/software may also beprovided which can be loaded and run to achieve this effect.

FIG. 23 illustrates schematically an example of displaying data relativeto an image of a blood vessel, such as a coronary artery.

FIG. 23( a), (b) and (c) illustrate respectively for the same length ofblood vessel three different individual/groups or other combinations ofmolecules or biomarkers associated with different stages in plaqueevolution. The stages of the various plaques found as a result of thedetected release are shown at positions relative to the length of theblood vessel.

A blood vessel is shown schematically in transfer section with a seriesof boxes overlayed onto it, each box representing a sampling location.

The different molecules can be analysed and linked to stages in plaquedevelopment so as to create a risk assessment profile. In theillustrated example, early stage, vulnerable and stable plaques areshown. Those different stages can be illustrated in different respectiveforms, for instance with different respective intensities or colours.The intensity or colour in each example can then show the amount ofrelease and hence the scale threat of any plaque.

It is proposed that this technique could be used to determine theeffectiveness of clinical therapy. In particular, the number and extentof truly vulnerable plaques could be assessed over time.

The approach could also be used to develop proprietary biomarkers. Theapproach allows the collection and interpretation of accurate molecularinformation. Molecular data may be obtained and analysed at multiplepoints throughout a patient's therapy (and indeed with multiplepatients). In this way, it becomes possible to make a correlationbetween molecular expression and clinical outcome. By using thisinformation, it becomes possible to identify molecules having biomarkerpredictive status.

The analysis can also be used to provide information regarding theimpact of local device-based therapy, such as stenting or angioplasty.In particular, it is possible to assay and analyse molecules associatedwith damage, such as inflammatory processes or the release ofendothelial wall material. It is then possible to provide accurateassessment of the extent and location of damage and, if used again, itsrecovery.

FIGS. 24( a) and (b) and 25(a) and (b) illustrate respectively theconcentration of biomarker present at the central region C of a bloodvessel V as a result of plaque P.

FIG. 24 illustrates the case where little or no mixing occurs within theblood vessel V. As illustrated in FIG. 24( a), the concentration ofbiomarker takes the form of a plume drifting and then graduallyspreading within the flow of blood in the blood vessel V. As illustratedin FIG. 24( b), when the plume reaches the centre C of the blood vesselV, the detected concentration of biomarker rises very rapidly to arelatively high concentration. However, the detected concentration thenalmost immediately starts to drop. Indeed, as the plume spreads outalong the blood vessel, the detected concentration will gradually dropto the concentration where the biomarker is spread evenly throughout thecross-section of the blood vessel as indicated by the dashed line E.

FIG. 25( a) illustrates somewhat schematically how a biomarker isdistributed in the flow of blood in the blood vessel V when mixing isused. In particular, depending upon the efficiency of the mixing, thebiomarker will very rapidly spread across the entire cross section ofthe blood vessel and reach the even distribution indicated in FIG. 25(b) with dashed line E. When the biomarker distribution first reaches thecentral region C, it will already have been mixed significantly and,hence, will not be at the high concentrations discussed above for FIG.24. In fact, it is likely only slightly to exceed the even distributionE before rapidly lowering to that even distribution.

In either the unmixed or mixed example, it will be seen that the firstdetected position of the biomarker is always downstream of the actualplaque P. For the unmixed example of FIG. 24, the length of offset isconsiderably greater and also the predictability of that offset islower.

For either case, it is proposed to introduce an additional step betweenobtaining the corrected concentration data for the biomarkers anddisplaying that information, for instance as illustrated in FIG. 23. Inparticular, it is proposed to introduce an additional correction withregard to offset. Taking into account factors such as blood vesseldiameter, flow rates and catheter properties, it becomes possible tooffset the displayed concentrations such that they are located relativeto the image of the blood vessel in positions more representative of theactual positions of any plaque, etc.

Because, as mentioned above, the offset for a mixed flow is much shorterand more predictable, the mixed flow has significant advantages. Whencorrecting the offset for mixed flow, the characteristics of the mixingcan be taken into account. In particular, the accuracy of localisationof biomarker release relative to the position in the artery can beincreased by using knowledge of the way by which the mixers interceptand divert flow from the boundary layers of the blood vessel tocollection ports along the elongate central body of the catheter.

So far, consideration has been given only to actually detected (andcorrected) values. However, when samples are to be analysed that weretaken from a catheter using mixing, those actual values are generallysmaller and provide more of a step change than a peak for identificationby the user.

In view of this, it is also proposed to take a differential of thecorrected concentration values for the biomarkers.

Where mixing is employed, the mixed concentration of biomarker isreached very rapidly. In comparison, where mixing is not used, theconcentration is somewhat variable. By taking a differential of thevalues, a very clear indication of initial detection of a biomarker canbe obtained. Resulting differential values can be displayed asillustrated in FIG. 23 and, additionally, can be corrected for offset inthe manner discussed above.

1. A catheter for taking a plurality of samples from within a length ofa blood vessel, the catheter including: an elongate central bodyarranged to be inserted into and positioned along a blood vessel; atleast one collection area defined along the elongate central body forcollecting samples at the central region of the blood vessel; and atleast one mixer provided radially outwardly of the elongate central bodyand arranged to create a flow of blood from a boundary layer at a wallof the blood vessel to the elongate central body so as to enable the atleast one collection area to collect samples from the boundary layer. 2.The catheter according to claim 1 wherein the at least one mixer is astatic mixer.
 3. The catheter according to claim 1 wherein the at leastone mixer is deployable from an inactive state in which the at least onemixer is close to the elongate central body for insertion into a bloodvessel to an active state in which the at least one mixer is furtheraway from the elongate central body so as to interfere with a boundarylayer of the blood vessel.
 4. The catheter according to claim 1 whereinthe at least one mixer extends circumferentially around the elongatecentral body in substantially all radial directions.
 5. The catheteraccording to claim 1 wherein the at least one mixer comprises arespective plurality of mixing elements extending radially from theelongate central body.
 6. The catheter according to claim 5 wherein eachmixing element is pivotably attached to the elongate central body so asto pivot in the elongate direction of the elongate central body andtowards and away from the elongate central body.
 7. The catheteraccording to claim 5 wherein each mixing element has the form of apaddle extending in radial and tangential directions with respect to theelongate central body.
 8. The catheter according to claim 5 wherein eachmixing element has a planar extent following a respective plane througha respective diameter of the elongate central body.
 9. The catheteraccording to claim 5 wherein the mixing elements are arranged atsuccessive positions along the elongate central body and atcorresponding successive angles around the elongate central body. 10.The catheter according to claim 9 wherein the relative angle around theelongate central body between mixing elements at adjacent positionsalong the elongate central body is substantially 90°.
 11. The catheteraccording to claim 9 wherein the mixing elements are arranged in pairs,each pair of mixing elements being positioned at a respective positionalong the elongate central body and individual mixing elements of a pairof mixing elements being on opposite respective sides of the elongatecentral body.
 12. The catheter according to claim 11 wherein the atleast one mixer includes at least two pairs of mixing elements.
 13. Thecatheter according to claim 9 wherein the mixing elements are spaced andshaped such that when mixing elements at adjacent positions along theelongate central body are deflected so as to be substantially parallelwith an outer surface of the elongate central body, the mixing elementsat adjacent positions substantially do not overlap.
 14. The catheteraccording to claim 1 wherein the at least one collection area includesat least one collection port located at a respective position along theelongate central body for collecting a respective sample at thatposition.
 15. The catheter according to claim 14 wherein the elongatecentral body includes at least one lumen extending internally along theelongate central body connecting with the at least one collection port.16. The catheter according to claim 15 wherein the elongate central bodyincludes a plurality of lumens extending internally along the elongatecentral body connecting with respective collection ports.
 17. Thecatheter according to claim 14 wherein at the at least one collectionarea, the elongate central body includes an outer wall having anoutwardly facing surface and an inwardly facing surface and an innerbody in which the at least one collection port is defined, the inwardlyfacing surface of the outer wall and the inner body defining acircumferential gap therebetween and a circumferential array of throughholes being defined through the outer wall between the inwardly facingsurface and the outwardly facing surface such that the circumferentialgap forms a manifold feeding the at least one collection port from aplurality of radial directions.
 18. The catheter according to claim 1including a plurality of mixers arranged along the length of the centralbody wherein collection areas are defined between said mixers.
 19. Thecatheter according to claim 18 wherein at least one collection area isdefined between adjacent mixers.
 20. The catheter according to claim 18where a collection area is defined at one end of the catheter so as tobe upstream of any mixer when in use.
 21. The catheter according toclaim 1 further comprising a sleeve within which the elongate centralbody and the at least one mixer can be stowed, the sleeve beingwithdrawable so as to expose the at least one mixer and the at least onecollection area.
 22. A method for generating a data profile for one ormore biomarkers emanating from the wall of a blood vessel, which methodcomprises analysing a plurality of blood samples from a bloodstream thathas been mixed substantially across the radial extent of the bloodvessel to include blood present in the boundary layer at the bloodvessel wall, the blood samples being taken at respective locations alonga length of the blood vessel, the analysis including the steps of:measuring a concentration level of a biomarker in each blood sample;determining a first concentration correction factor for each respectiveblood sample to correct for differences in sample volume and dilutionbetween different blood samples; determining a second concentrationcorrection factor to correct for a measured background concentrationlevel for the biomarker present in general circulation within thebloodstream; for each blood sample, applying a respective first and thesecond concentration correction factor to the measured concentrationlevel of the biomarker in each blood sample to determine a correctedconcentration level of the biomarker; and, generating a data profile ofcorrected concentration levels for the biomarker along the length of theblood vessel.
 23. The method according to claim 22, comprising the stepof analysing at least one blood sample collected from an upstreamlocation to determine the second correction factor to be applied to themeasured concentration levels of the biomarker.
 24. The method accordingto claim 22, in which blood samples are analysed to measure theconcentration of a reference marker in general circulation in thebloodstream having a known or measured concentration, whereby arespective first correction factor is calculated for each blood sampleto correct for differences between the measured concentration of thereference marker in the blood sample and that in general circulation.25. The method according to claim 22, comprising blood samples takenfrom within a coronary artery and at least one blood sample taken froman aortic arch.
 26. A method of profiling a length of a blood vessel todetermine the pathological state or physiological state of the bloodvessel wall, comprising the steps of: introducing into a blood vessel aflexible vascular catheter having a body section provided with aplurality of blood collection ports for collecting samples along alength of the blood vessel; deploying at least one mixer radiallyoutwardly of the catheter body, the mixer thereby mixing bloodsubstantially across the radial extent of the blood vessel to includeblood present in a boundary layer at the blood vessel wall; collectingblood at the blood collection ports downstream of the at least onemixer; analysing blood collected by the blood collection ports of thecatheter to determine a data profile of the concentration levels of oneor more biomarkers along the length of the blood vessel.
 27. A method ofsampling blood in vivo from a blood vessel, comprising the steps of:introducing into a blood vessel a flexible catheter having a bodysection provided with a plurality of blood collection ports forcollecting samples along a length of the catheter; deploying at leastone mixer radially outwardly of the catheter body, the mixer therebymixing blood flowing within the blood vessel substantially across theradial extent of the blood vessel; and, collecting blood at one or moreblood collection ports positioned downstream of the mixer for subsequentanalysis.